Identifying the position of the rotor of a wound-rotor synchronous machine may be useful for control of the machine in both motoring and generating operational modes. During initialization or startup of synchronous machines, estimating the initial position of the rotor relative to the stators of the machine is desirable for controlling the switching means of the current supplied to the machine. This information may be beneficial for improving the performance of the synchronous machine. For example, the initial position of the rotor may be particularly useful for starting the synchronous machine at maximum torque.
Some synchronous motor systems incorporate sensors, such as encoders and/or resolvers for determining the position of the rotor. However, the presence of an encoder or resolver may increase manufacturing costs and system complexity. Furthermore, these additional components may experience noise interference and performance degradation due to environmental conditions.
One solution for identifying the initial rotor position is described in U.S. Pat. No. 7,233,123 B2 (“the '123 patent”). The '123 patent is directed to a method and system for identifying the position of magnetic poles of a rotor of a multi-phase electrical machine relative to a stator of that machine. The method includes the steps of applying a voltage pulse to stator windings of each phase, sensing current flow in the stator windings of each phase due to the application of the voltage pulse to the respective stator windings, and determining the position of the magnetic poles of the rotor relative to the stator using the sensed current flow in the stator windings of each phase. The method is characterized in that the phases of the stator windings are star-connected at a neutral junction, and the voltage pulse is applied to the stator windings of each phase in parallel.
The solution provided by the '123 patent may suffer from a number of possible drawbacks. For example, the '123 patent may only provide a solution for motors with star-connected stator windings and a permanent magnet rotor. Furthermore, the systems and methods proposed in the '123 patent require a wait time to ensure any current flowing in the windings has decayed to zero before applying the voltage pulse. Additionally, the methods and systems in the '123 patent observe the machine inductances, which is only observable in machines with salient features that provide information related to magnetic north or south of the rotor windings.
The presently disclosed systems and methods are directed to overcoming and/or mitigating one or more of the problems set forth above and/or other problems in the art.